The present invention relates to the field of medical devices, and more particularly to catheters, dilatation balloons, and the like.
Atherosclerotic cardiovascular disease is common, and is caused by a narrowing of the arterial lining due to atherosclerotic plaques. Balloons mounted on the distal ends of catheters are commonly used in the medical treatment of atherosclerotic diseases. Such balloons may be used for dilating lesions or blockages by compressing plaque, for recanalizing and dilating a diseased vessel, and for expanding prosthetic devices such as stents at a desired location in a bodily vessel. The requirements for strength and size of the balloons vary widely depending on the balloon's intended use and the vessel size into which the catheter is inserted.
Percutaneous transluminal coronary angioplasty, or balloon angioplasty, is a non-invasive, non-surgical means of treating peripheral and coronary arteries. This technique consists of inserting an uninflated balloon catheter into the affected artery. Dilation of the diseased segment of artery is accomplished by inflating the balloon which pushes the atherosclerotic lesion outward, thereby enlarging the arterial diameter. The balloon is then deflated and the catheter is withdrawn.
Cutting balloons are another type of medical balloon which have cutting edges, also referred to as atherotomes or blades for recanalizing and dilating a diseased vessel, and facilitating balloon angioplasty procedures.
In any applications such as the above, the balloon traverses a tortuous anatomy as it is being delivered to the location in extremely small bodily vessels and used to open stenoses of blood vessels by balloon inflation, or for delivery of medical devices, for example. In these applications, it is desirable for the balloon to assume as low a profile, i.e. the outer diameter of the balloon, as possible. Considerable effort has been put forth in the development of medical balloons with a low profile by minimizing the dimensions of the shape-form or the inner tube which extends through the balloon to its distal end, and by reducing the wall thickness of the balloon itself.
Several methods have been employed to reduce the profile of the dilatation catheter including manipulating the wall thickness of the balloon material by o developing ever thinner walled balloons, while still retaining the necessary distensibility and burst pressure rating, so as to permit lower deflated profiles.
The profile of the deflated balloon is limited by the thickness of the waist and cone portions of the balloon. Usually, the waist and cone wall thicknesses are thicker than that of the body of the balloon due to the smaller diameter of the waist and cone portions. Thus, a reduction in thickness of the waist and cone portions can reduce the profile.
Balloon forming techniques involve stretching and blowing of the balloon from a segment of extruded polymer tubing. Balloons produced by stretching and blowing a balloon preform or “parison” can have thicker waist and cone walls than the wall thickness of their body portions. It is desirable to reduce the thickness of the cone walls which contribute to the overall thickness of the catheter, to allow for improved tracking, crossing and recrossing of lesions, and to improve refolding after use to facilitate withdrawal of the balloon catheter.
One method of reducing the cone or waist thicknesses of a balloon has been by laser ablating material from the cone or waist. This is disclosed in U.S. Pat. No. 5,826,588, the entire content of which is incorporated by reference herein.
Other methods are disclosed in commonly assigned U.S. Pat. No. 6,193,738, the entire content of which is incorporated by reference herein.
Thus for such applications, thin walled, high strength, relatively inelastic balloons of predictable inflation properties are desired. However, this combination of properties, i.e. thin walls and low resilience, may have increased susceptibility to pin hole formation and ruptures. Stronger balloon materials having greater wall thickness may be employed to increase balloon robustness, but this can also decrease balloon flexibility.
There remains a need for a balloon having improved abrasion resistance and resistance to rupture during use, without sacrificing flexibility, which is not subject to pin holes during the molding process and is readily collapsible to a small diameter upon deflation.